Disclosed is a method for controlling an exhaust gas purification device, wherein the regeneration operation includes main regeneration operation for detaching the nitrogen oxides adsorbed onto the nitrogen oxide adsorbing material, the method comprising: operating the first combustion device and the second combustion device while the exhaust gas is prevented from flowing into the branch exhaust passage subjected to the regeneration operation by the switching of a changeover valve during the regeneration operation; and decreasing the flow rate of the first mixture gas as the stage of the main regeneration operation advances.